1. Field of the Invention
The present invention relates generally to gas container assemblies, and particularly to an improved coupling for interconnecting a gas container having an integral regulator with other equipment such as a flow meter, flow indicator or delivery apparatus.
2. Related Art
The present invention finds particular utility in the medical field, where it is frequently required to deliver a gas, such as oxygen, or a mixture of gases to a patient for inhalation. In such circumstances a large volume of gas is required, for which reason the container (usually in the form of a cylinder) is filled with gas under considerable pressure (for example between 137 and 300 bar) and the outlet is provided with a pressure regulator which delivers the gas to the delivery apparatus at a pressure suitable for such apparatus, typically in the region of 4 bar.
Basic gas cylinders for this purpose are simple containers or vessels with an on/off valve and a connection port by which the pressure regulator can be fitted thereto. The pressure regulator itself has an outlet connection to allow the delivery apparatus to be connected thereto.
One problem which has occurred frequently in the use of pressurized gas containers of this type, especially those delivery oxygen, is the risk of fires which are generally initiated by the introduction of hydrocarbons and/or debris at the high pressure interface between the cylinder and the external regulator. For this purpose gas canisters or cylinders with permanently fitted or integral regulators and flow meters have been developed over recent years. In this context, the term “integral” as applied to pressure regulators will be understood to include those which are attached in such a way that they are difficult to remove or impossible to remove without specialist equipment. The flow meter is required for many uses as it provides an accurate, metered flow of the gas based upon the stable pressure derived from the regulator downstream from which the flow meter is fitted. It will be appreciated that in the medical environment patients are prescribed a specific flow rate of gas not a specific pressure of gas, and the flow meter provides this controlled flow rate.
Although this meets the fire risk it has attendant disadvantages, not least of which are the economic penalties of complex equipment. A gas canister fitted with an integral regulator and flow meter is obviously more expensive to produce and involves a greater ongoing “carrying” cost than merely a plain gas canister or cylinder since the additional cost of providing the regulator and flow meter must be borne over the length of the life of the container. In this connection it will be appreciated that such gas canisters or cylinders are very robust and intended for repeated filling, for which purpose an infrastructure of refill stations and delivery and return operations have been developed. At the refill stations a large quantity of empty canisters are stored, filled, or ready for refill, and subsequent delivery to fresh destinations. Because there is a wide range of flow rates required for different gases and different medical conditions, as well as a range of differences between gas cylinders, such as those designed for infant use and those designed for adult use (infants typically require flow rates in the region of one tenth of the flow rates required by adults) as well as different capacities, this involves maintaining a wide range of cylinders of different sizes fitted with flow meters having different ranges of flow rates, and this naturally results in an increase in the costs of the operation.
It would be a valuable advantage, therefore, to be able to interchange at least the flow meter component of a gas cylinder in order to be able to make use of a standardized cylinder and regulator combination whilst nevertheless maintaining the opportunity to provide a wide range of flow rates without compromising the fire safety inherent in the use of an integral regulator.